Japanese Model Publication No. 25561/1982 discloses a conventional starter motor of this type as shown in FIG. 1.
In the figure, a casing (1) is composed of a cylindrical yoke (2) and front and rear receivers (3) and (4) mounted on opposite ends of the yoke (2), respectively, and a field core (5) and a field winding (6) are mounted within the yoke (2). A rotary shaft (7) is rotatably supported by the front receiver (3) and the rear receiver (4) through respective bearings (3a) and (4a). An armature (8) is fixedly mounted on the rotary shaft (7) opposite the field core (5) with a predetermined space therebetween, and a pinion (9) for transmitting rotational force generated in the armature (8) to a starter gear (10) coupled to a drive shaft (not shown) of an engine and an over-running clutch (11) for transmitting the rotational force of the armature (8) to the pinion (9) unidirectionally are mounted on the rotary shaft axially slidably. One end of a lever (12) engages with a sleeve portion (11a) of the over-running clutch (11) and the other end of the lever (12) engages with a rod (13a) of an electromagnetic switch (13) mounted on the front receiver (3), so that, when the rod (13a) is moved leftwardly by the electromagnetic switch (13), the one end, i.e., the lower end of the lever (12) moves rightwardly with a point A as a fulcrum to apply rightward movements to the over-running clutch (11) and the pinion (9). The electromagnetic switch (13) is powered through a starter switch (not shown) of the engine to attract the rod (13a) leftwardly by an electromagnetic mechanism provided therein to thereby close contacts (not shown) provided therein so that electric power is supplied to the field winding (6) and the armature (8).
In the conventional starter motor as constructed above, when the starter switch is closed, the electromagnetic switch (13) is actuated to move the over-running clutch (11) and the pinion (9) rightwardly so that the pinion (9) meshes with gear (10). On the other hand, simultaneously with this operation, the contacts in the electromagnetic switch (13) are closed to power the field winding (6) and the armature (8), causing the armature (8) and the rotary shaft (7) to rotate unidirectionally as a unit. This rotational force is transmitted through the over-running clutch (11) to the pinion (9) and then to the gear (10) to start the engine.
In such conventional starter motor, when an automobile on which the starter is mounted is used in low temperature areas and if a sealing of a joint portion between the front receiver (3) and the engine is not adequate, the gear (10) which is possibly partially exposed may catch up ice and/or snow piled up on the ground while the engine is operating. Ice and/or snow caught up may fill a gap between the bearing portion (3a) of the front receiver (3) and the pinion (9), which may be frozen and solidified after the engine stops. Due to solidified ice and/or snow, the pinion (9) can not move rightwardly even if the starter switch is closed subsequently and the electromagnetic switch (13) is actuated thereby, and thus the pinion (9) can not mesh with the gear (10). In such case, the contacts in the electromagnetic switch (13) are closed to rotate the armature (8). However, the pinion (9) merely rotates in a slip engagement between an end face thereof and solidified ice, without transmission of rotational force to the gear (10). That is, with such conventional starter motor, the pinion (9) can not mesh with the gear (10) due to solidified ice deposited between the bearing portion (3a) of the front receiver (3) and the pinion (9), resulting in an impossibility of engine starting.
The present invention overcomes such problem by providing a starter motor capable of removing solidified ice and/or snow deposited in the front receiver by rotation of the pinion.